/Engine/Source/Runtime/RenderCore/Public/VertexFactory.h
Calls the function ptr for the shader type on the given environment
void ModifyCompilationEnvironment ( const [FVertexFactoryShaderPermutationParameters](API\Runtime\Renderer\FVertexFactoryShaderPermutationP-) & Parameters, [FShaderCompilerEnvironment](API\Runtime\RenderCore\FShaderCompilerEnvironment) & OutEnvironment ) const